Transcriptional Regulation of the Placental Lactogen Genes in Mouse Trophoblast Giant Cells

The placenta is the site of synthesis of several members of theprolactin (PRL)/growth hormone (GH) family in rodents, ruminants, and primates (1). In the mouse these placental hormones includeplacental lactogen I (mPL-1) andplacental lactogen II (mPL-11), proteins that bind to the PRL receptor and have PRL-like bioactivities. By binding to the PRL receptors, mPL-I and mPL-II participate in the regulation of a number of pregnancy-specific changes in the mother, including changes in ovarian steroidogenesis, liver metabolism, and mammary development (1). Since these hormones also enter the fetal circulation, they may also participate directly in embryonic development (1). Other closely related proteins with unknown physiological function,proliferin (mPLF) andproliferin related protein (mPRP), are also synthesized in the mouse placenta.